In the previous post, we have discussed on the 1st criterion for predicting the products of electrolysis for Aqueous Solutions, that is to determine the Position of Metals In The Reactivity Series.

Today, we are going to look at the 2nd criterion, that is:

Effect of Concentration of Solution on Effective Discharge

• It applies only to ANIONS
• Only for Concentrated Solutions
• An increase in the concentration of an anion tends to promote its discharge

Example:

Consider Electrolysis of concentrated NaCl solution using carbon electrodes.
2 types of anions are attracted to the anode: Cl- and OH- ions

According to the reactivity series, OH- ions should be discharged preferentially (as we have seen in the previous post on diluted aqueous solutions). However, Cl- ions are far more numerous than OH- ions and so are discharged instead.

Try out this question to see if you understand this concept.

Question:

What would you observe when a concentrated solution of HCl is electrolyzed using Platinum electrode? Explain your observations and write down the equations involved.

PS: Remember to leave down your comments and suggested answers in the “Leave Your Reply” section below.

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